How to designate a viewport for one camera?
Blender only allows one active camera in a scene and numpad 0 moves the view to the active camera, so you can't setup a different camera view for each viewport.

You can setup as many viewports as you want and you don't have to be viewing from a camera in each viewport. Blender includes an addon called stored views which gives you a way to bookmark multiple viewport locations, this can provide an easy way to set a viewport back to a desired viewing location, similar to what you would get from a camera.